Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$123.47	6.722%	$131.7697	$131.77	$131.75	$131.80
Purchase #2	$107.98	12.700%	$121.6935	$121.69	$121.70	$121.70
Purchase #3	$112.88	5.299%	$118.8615	$118.86	$118.85	$118.90
Purchase #4	$238.85	6.286%	$253.8641	$253.86	$253.85	$253.90
Purchase #5	$91.40	4.659%	$95.6583	$95.66	$95.65	$95.70
Purchase #6	$233.90	9.488%	$256.0924	$256.09	$256.10	$256.10
Purchase #7	$41.94	10.609%	$46.3894	$46.39	$46.40	$46.40
7 purchase totals =	$950.42		$1,024.3289	$1,024.32	$1,024.30	$1,024.50